Method for bleaching cotton and analogous textile fibers



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Patented May 3, 1938 UNITED STATES PATENT OFFICE METHOD FOR BLEACHING COTTON AND ANALOGOUS TEXTILE FIBERS Hugo Weiss, Augsburg, Germany No Drawing. Application June 29-, 1934, Serial No. 733,116. In Germany July 10, 1933 1 Claim.

This invention relates to improvements in the bleaching of cotton and analogous fibers.

The bleaching of cotton by means of bleaching baths containing caustic alkali and peroxide compounds with or without a combination of a chlorine bleaching bath is well known.

In all these processes the materials are cleansed before bleaching. This cleansing generally consists of desizing and boiling. This also applies to processes in which old peroxide bleaching baths which still contain active oxygen are employed for the desizing.

It is also known to bleach cotton by first desizing then using peroxide bleaching baths to which caustic alkalies have been added and in addition as a further aid to bleaching to use a chlorine bleaching bath. In such a combination of baths the "caustic boil is omitted.

The object of this invention is a process in which the boil is inserted between two bleaching processes in which for instance a first bleaching process consists in a treatment of the singed or unsinged goods with a bleaching agent capable of splitting oil oxygen, as for example, a per oxidg bath, to which gapstic alkalihas been added and whiclfis'carriedout sd'inte nsively, that the subsequent boiling process has an incomparably better cleansing effect than that of any other boiling process which has been used up to the present. The boil in this case is so penetrating and efiective that it is easy to finish the bleach after the boil either by a short treatment with a peroxide bleach bath to which caustic alkali has been added or with a hypochlorite bleach.

In the suggested process the first peroxide bleach is not merely a desizing, as used in well known cotton bleaching methods; but it has been proved that, apart from the much longer duration of such bleach processes, it was impossible, when omitting the boiling process, to produce the same degree of purity and cleanness. The reason being that it is not sufficient to remove the husks in order to get a clean white; on the contrary it is absolutely necessary, that the fatty and waxy materials should also be removed. The latter can only be removed in the boil, as is proved in many experiments.

Therefore all process eliminating the boil could only be used in practice in a limited Way.

By the new process it is possible very satisfactorily to bleach different kinds of cotton, both thin as well as thick qualities, and single or mixed.

Peroxide bleaching baths, which are used before and after the boil, may consist for instance of solutions of sodium peroxide and hydrogen peroxide in the presence of waterglass and if desirable with the addition of other stabilizers or wetting out agents In place of sodium peroxide, caustic alkali and hydrogen peroxide can be used. M

For both peroxide bleaching processes the best temperature lies between and Celsius.

Thus, the bleaching cycle will consist of (l) (a) Caustic alkali peroxide bath.

(b) Boil. (c) Caustic alkali peroxide bath.

( (a) Caustic alkali peroxide bath.

(1)) Boil.

(c) Chlorine bleaching bath. 

